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Am J Med Genet B Neuropsychiatr Genet. 2015 Sep;168(6):406-413. doi: 10.1002/ajmg.b.32335. Epub 2015 Jun 30.

Heritability of attention-deficit hyperactivity disorder in adults.

Author information

1
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.

Abstract

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. Symptoms often persist into adulthood, with a prevalence of 2.5-5% in adult populations. Twin studies in childhood consistently report high heritabilities of 70-80%, while studies in adult samples show only moderate heritability of 30-40% when estimated from self-ratings. This review summarizes the available research on the heritability of ADHD in adults. Three key findings are outlined: (i) self-ratings lead to relatively low heritability estimates of ADHD, independent of age and whether ratings refer to current or retrospective symptoms; (ii) studies relying on different informants to rate each twin within a pair (i.e., self-ratings and different parents/teachers rating each twin in a pair) consistently yield lower heritability estimates than studies relying on ratings from a single informant; (iii) studies using cross-informant data via either combined parent and self-ratings or clinical diagnoses information suggest that the heritability of ADHD in adults could be as high as 70-80%. Together, the reviewed studies suggest that the previously reported low heritability of ADHD in adults is unlikely to reflect a true developmental change. Instead, the drop in heritability is better explained by rater effects related to a switch from using one rater for both twins in a pair (parent/teacher) in childhood, to relying on self-ratings (where each twin rates themselves) of ADHD symptoms in adulthood. When rater effects are addressed using cross-informant approaches, the heritability of ADHD in adults appears to be comparable to the heritability of ADHD in childhood.

KEYWORDS:

adult ADHD; genetics; rater effects; twin studies

PMID:
26129777
DOI:
10.1002/ajmg.b.32335

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